Genetic diversity assessed by SSR markers and chemotyping of Fusarium culmorum causal agent of foot and root rot of wheat collected from two different fields in Tunisia

Abstract

Fusarium culmorum is a major pathogen able to cause foot and root rot and the incitant of Fusarium head blight in wheat in Tunisia. The aims of the present study were to evaluate by PCR the type of mycotoxins produced, to determine the mating type and to analyse the genetic diversity by microsatellite markers of 82 F. culmorum isolates recovered from two separated Tunisian fields. Specific sequences in the Tri6-Tri5 intergenic region, Tri7 and Tri13 were used to identify 3-AcDON- or 15-AcDON-. All studied F. culmorum isolates, were of the 3-AcDON- type. No 15-AcDON- and NIV types were detected in this research. Both mating types MAT1-1 and MAT1-2 were recovered from the two fields in approximately equal proportions. Five polymorphic microsatellite markers were applied to F. culmorum isolates, to determine the genetic variation in and among populations. Sixty-four haplotypes were identified; the analysis of the population structure did not reveal a strong variation between fields. Total gene diversity (H T = 0.505; H S = 0.497) and analysis of molecular variance confirmed that most of the genetic variability was within populations (Φ ST = 0.033; P < 0.0039). Gene flow (N m = 31.05) indicated little differentiation among populations. Based on these results, the F. culmorum isolates collected from different fields might be part of one large panmictic population and in addition the low linkage disequilibrium values with high genetic variation within populations suggest that the population is recombining sexually.